Fourdrinier wire and method of making the same



Feb. 18, 1964 E. H. HALL, JR 3,121,660

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BY W5 ATTOR N EYS United States Patent,

3,121,660 FOURDRIWER WERE AND METHOD 0F MAKZNG THE SAME Edward H. Hall, Jr., 424 Sunny Hill Road, Lunenhurg, Mass. Filed Feb. 13, 1961, Ser. No. 89,019 3 Claims. (til. 162348) This invention pertains to paper manufacture, more particularly to a screen or pervious carrier for the separation of liquid from fibrous paper stock, one example of such a carrier being the endless band of screen material, commonly termed a Fourdrinier wire, employed at the wet end of a conventional Fourdrinier paper-making machine and upon which the paper web is initially formed. A further example of said carrier is that which forms the peripheral covering for the cylindrical screen drum employed in certain paper-making machines.

The customary Fourdrinier wire is of fine mesh fabric Woven from metallic wire. Customarily this wire is a copper alloy, although stainless steel, andmore recently synthetic strands, such as nylon, have been employed in weaving such a web, these materials being selected to resist corrosion by the acids present in paper stock. Since the Fourdrinier wire is used as a drive belt for some of the cylinders about which it passes, it is subjected to severe tensional stresses and to rapid frictional wear where it is dragged across the suction box cover while pulled down against the latter by the suction. For example, it requires a pulling stress of the order of 2,000 pounds. to draw the wire of a 200" paper machine across a single suction box, using a 7" suction. Since many paper machines use several suction boxes in series it is readily apparent that the longitudinal pull to which the Fourdrinier wire is subjected is very substantial. The, frictional resistance to motion of the wire is in part due to the fact that the wire is usually a one-and-one weave, wherein each strand of wire of one set passes alternatively over and under the wires of the other set, so that the surface of the wire is composed of a multitude of small projecting bights. Since these bights are the parts of the Fourdrinier wire which actually contact the suction box cover, they are rapidly abraided withthe result that the life of the customary Fourdrinier wire is very short, for example, two or three weeks and, since such wires are expensive to make, the maintenance of these wires constitutes a major item in paper-making costs.

Efforts to improve the paper-making machinery to insure longer life of .the Fourdr-inier wire have not heretofore been successful. For example, the use of heavier metal strandsresults in a coarser mesh such that the wire leaves marks on the paper, while reduction of the amount of suction sends the paper to the felt with an abnormal amount of moisture.

The present invention has for objects the provision of a pervious carrier which, although not made of wire, performs the function of a Fourdrinier wire (and which for convenience will herein be referred to as a Fourdrinier wire), but which has a longer effective life than the customary woven Fourdrinier wire; to provide a Fourdrinier wire having a surface which is smoother than that of the customary woven Fourdrinier wire; to provide a Fourdrinier wire which is less subject to corrosion by the acid found in the paper stock than the customary bronze wire; to provide a Fourdrinier wire which may be manufactured at substantially less expense than the usual prior wire; t3 provide a Fourdrinier wire such that frictional resistance to its motion is lessened as compared with that developed by theusual wire, thereby greatly prolonging the life of the wire as compared with prior practice and reducing the cost of power necessary to drive the wire, while decreasing 3,121,660 Patented Feb. 18, 1964 the wear on the suction box cover, all without lowering the quality of the paper produced, or slowing down its production.

Other and further objects and advantages of the invention will be pointed out in the following more detailed description and by reference to the accompanying drawings, wherein:

FIG. 1 is a fragmentary diagrammatic plan view of a piece of Fourdrinier wire embodying the present inventron;

FIG. 2 is a section, to larger scale, on line 22 of FIG. 1;

FIG. 3 is a fragmentary plan view illustrating one face of a piece of sheet material, wherein, in accordance with one preferred mode of preparing Fourdrinier wire in accordance with the present invention, the material has been provided with apertures by a punching operation;

FIG. 4 is a section on the line 4-4 of FIG. 3;

FIG. 5 is a view similar to FIG. 3, showing the appearance of the opposite face of the sheet material, that is to say, that face from which the punches emerge;

FIG. 6 is a view similar to FIG. 4, but showing the sheet material after its surface has been finished to remove the burrs left by the punches;

FIG. 7 is a section, to larger scale than FIG. 5, illustrating sheet material which has been provided with perforations, for example, in accordance with the procedure illustrated in FIGS. 3 to 6, but which has subsequently been so coated with a material (which forms a tough and hard surface) as to reduce the effective size of the original perforations, while, at the same time, protecting the sheet material from contact with corrosive substances and providing a very smooth slippery surface for contact with the suction box covers;

FIG. 8 is a fragmentary plan view, to larger scale than FIG. 5, showing how the edges of two pieces of perforated sheet material may be arranged and united to form a longer sheet and illustrative ofone procedure whereby several sheets may be joined to form an endless band or Fourdrinier. wire;

FIG. 9 is a section on the line 9-9 of FIG. 8;

FIG. 10' is a composite plan view diagrammatically illustrating fragmentary portions of sheet-material Fourdrinier wire according to the present invention, indicating, by way of example, the possibility. of arranging. the perforations according to -a variety of patterns;

FIG. 11 is a fragmentary plan view showing a preferred pattern of perforations and dimensional relationships;

FIG. 12 is a diagrammatic plan view illustrative of one way of joining perforated sheets to form an endless band of the desired width;

H6. 13 is a view similar to FIG. 12 showing a modified arrangement;

FIG. 14 is adiagrammatic elevation showing the improved Fourdrinier wire in use; and

FIG. 15 is a diagrammatic vertical section illustrative of the use of sheet material like that of FIG, 6, for example, for covering the peripheral surface of the cylinder of a cylinder-type machine.

Referring to the drawings, FIG. 14 shows an endless Fourdrinier wire W, according to the present invention, installed in a paper-making machine having a conventional flow box F and suction boxes B, B

Referring to FIG. 1, the numeral lll designates afrag- .mentary portion of a Fou-rdninier wire made in accord ance with the present invention, showing one lateral edge of the wire at M and showing the wire as having parallel rows of small perforations 11, the perforations in each individual row being uniformly spaced apart and adjacent rows being so arranged that their perforations are staggered relatively to each other. However, it is within the scope of the invention to arrange the perforations according to various patterns, as illustrated by way of example in HG. 10. Obviously, it is desirable to provide a maximum percentage of open area (that is the aggregate area of the perforations per unit of square of the sheet material), while employing individual perforations of a size suitable for the intended use and with due regard to the retention of enough of the original sheet material to insure adequate strength. A preferred arrangement, keeping these desiderata in mind, is illustrated in FIG.

11, wherein the perforations are initially of an internal diameter of 0.012.", and arranged in a 45 pattern with alternate rows spaced apart 0.021", both horizontally and vertically. Such an arrangement and diameter of perforation provides an aggregate open area of approximately 35.4% and without unduly weakening the sheet material. It appears that circular perforations of an internal diameter of from 0.005 to 0.015" may be useful according to the kind of paper stock being processed, and with an average diameter of approximately 0.010.

Since the marginal portion of the Fourdrinier wire cannot make perfect paper, it is preferred, in the present instance, to leave the margin 12 of the wire unperforated, for example, for a width of from /2 to 1%. inches. This unperforated margin with its smooth straight edge is less prone to develop edge cracks than the usual wire, pro- ,vides strength to resist longitudinal pull, and results in less wear from the guides and other parts with which it contacts. Preferably, these perforations are round, although holes of other shape may be used, if desired, and it is contemplated that the holes, as initially formed, may be larger than the desired final size, and at a later step reduced in effective diameter. The material in which the perforations 11 are formed may be of any suitable character having the requisite tensile strength and flexibility. For example, it may be of brass of the order of 0.005" thick, or may be synthetic plastic, for instance (but Without limitation), Teflon (a tetrafluoroethylene polymer, made by the Du Pont Company), or natural rubber, or other similar material, or combinations thereof.

While the holes or perforations in this sheet material may be provided in other ways, for instance by drilling, extrusion, or injection molding, it is at present believed that the most efiicient Way of forming these openings or perforations, is by a punching operation, preferably employing for the purpose a conventional roll feed perforating press, although a so-called fillet perforating machine may be employed.

The result of certain perforating processes, as illustrated in FIGS. 3, 4 and 5, is to form projecting burrs 16 at that face 15 of the sheet metal from which the tips of the punching dies emerge during the punching operation.

It is desirable for the attainment of certain objects of the invention, that the perforated sheet metal S be free from projections and that its faces be smooth, preferably polished and planar. Any appropriate method may be employed for imparting to the sheet metal the characteristics just referred to, for example the sheet may be subjected to a grinding operation. However, a preferred procedure is that known as electropolishing, which may be described as the reverse of electroplating, the sheet material being immersed in a suitable electrolyte and the current so applied as to remove material from the surface of the sheet. Since the action is most intense at any place where a part protrudes from the general surface of the sheet, the result of this operation is to remove projecting elements and eventually to produce a very smooth level surface. The result of this operation is illustraed in FIG. 6, where the two opposite surfaces 14a and 15a are shown as substantially plane and smooth.

The material thus prepared may, if desired, be employed in this condition in making up an endless band for use in a Fourdrinier machine, it being understood that it is contemplated, in accordance with the present invention that the perforated material will usually be prepared, first in sheets of convenient size for handling, and that such sheets will be assembled and united to form the endless belt structure which constitutes the entire Fourdrinier wire. For specific example, to make a Fourdrinier wire, according to the present invention, of a width of 384" and of a length of a coil of the selected material, for instance, sheet brass of the desired thickness and 48" Wide, is cut to provide eight lengths each 80" long. These lengths are then joined with the longitudinal edges of the adjacent lengths abutted to form a sheet 384" wide, the abutting edges of the adjacent sheets being integrally joined, for example, by silver-soldering, brazing, or electrowelding, and then the end edges of the resultant wide strip of material are abutted and similarly joined. The material may be perforated in the coil form, or the individual lengths may be perforated after cutting from the coil.

Assuming that sheets have been prepared as shown in FIG. 6, the union of two such sheets may be carried out as follows: Each sheet will be trimmed by a cutting operation extending transversely of the width of the sheet and in such a way as to bisect the holes 11 constituting one of the rows. Parts of two sheets S and S respectively, which have thus been trimmed are illustrated in FIG. 8, the half-holes resultant from such trimming being indicated at 11a and 11b. The two sheets are assembled so that the half-holes in the two sheets register to form a row of complete holes and the metal which intervenes between the assembled half-holes is then permanently united, for example, by the use of silver solder, indicated at K (FIG. 8). However, when perforations are arranged according to some patterns, it is readily possible to trim the material so that edges to be joined do not intersect perforations. Thus, as shown for example in FIG. 13, the longitudinal joint J uniting the lengths K and K of perforated material is located midway between adjacent longitudinal rows of perforations and, likewise, the end edges W and W (which will be joined in making the endless band), are spaced from the centers of the perforations of the respective adjacent rows a distance equal to one-half the spacing of adjacent transverse rows of perforations. On the other hand, in the arrangement shown in FIG. 12, both the longitudinal and transverse joints bisect perforations in the manner above described with reference to FIGS. 8 and 9.

Other methods of forming the joints, for example electro-Welding or brazing may be used, but whatever method is employed must be such that the union between the two sheets will not constitute an irregularity in the surface at the point of union so as to make a visible mark on the paper which is to be made by the use of the Fourdrinier Wire. It will be understood that enough individual perforated sheet will thus be united to provide an endless Fourdrinier wire of the desired length and width.

In order to improve the resistance of this novel Fourdrinier wire to the action of acids or other chemicals in the paper stock, it is preferred to coat the perforated material with a substance which is resistant to such chemical action and desirably such as will impart additional smoothness to the opposite faces of the sheet material. Desirably this coat-ing operation is performed after the perforated sheets have been assembled and united to form an endless band, although if the coating be by electroplating a metal onto the perforated sheet, it may be done either before or after assembly. Thus, for example, as- Surning that perforated sheets, such as the material shown in FIG. 6, have been assembled and united, the resultant endless band may be sprayed with a suitable protective medium, for example, a synthetic resin, preferably Teflon, which makes a good bond with the sheet material. The spraying operation is so performed that the opposite faces of the material receive a coating C of this material while, at the same time, the material coats the walls of the openings 11. The material selected should be one which, when it is cured or set, makes a strong and permanent bond with the material of the perforated sheet and pro:

vides a smooth, slippery, outer surface. Teflon, among other materials, has these characteristics. More than one coating may be applied in order to obtain the desired thickness. When Teflon is used, it is recommended that the perforated metal be oven-baked after each spray application at a temperature of about 720 F. to set and bond the coating to the metal. Since some of the coating material enters the openings 11, it forms a short, tubular liner element or tubule C for each of the openings 11, such liner element being integrally bonded at its ends to the coatings C at opposite sides of the sheet material. Thus, the sheet material is completely covered with this protective substance so that if desired, the sheet metal employed may be such :as would not ordinarily Withstand attack by the chemicals in the paper stock. If the coating be done by electroplating, then the plating metal should obviously be one which is resistant to corrosion.

Since the wall of the lining tubes C has appreciable radial thickness, the passages 11a through the liner element is of a lesser diameter than that of the original hole 11. This is advantageous since it is not necessary to make the holes in the metal sheet as small, initially, as the desired holes in the completed material. It is thus possible to use sheet metal of greater thickness than would otherwise be permissible since it is much more difficult to drill or punch very small holes in a given thickness of material than to form larger holes. Thus, in the instant case it is possible to use sheet metal which is thicker and thus capable of withstanding a greater tension stress than would be possible if it were necessary to punch the holes to their desired final effective diameter. Assuming as above suggested, that the holes are initially of a diameter of 0.012 as shown in FIG. 11, the coating may be of a thickness such that the effective diameter of each hole, in the coated material, is reduced to 0.010". It is contemplated that an initial diameter of the perforations between 0.005 and 0.015 would be satisfactory for most paper-making practices, with an effective open area of from 20% to 35.4%. While the coating may be of the same thickness on opposite sides of the perforated sheet, it may be preferable to coat the under or suction side of the sheet 50 as to provide a thickness greater than that at the upper side, thus better to withstand the frictional drag of the band across the suction box covers. For instance, the underside coating may be 0.005 in thickness and the upper coating 0.002" in thickness. Furthermore, this upper coating may be applied in two successive steps, each providing a coating of 0.001 in thickness. Since the coating material does not enter and coat the walls of the perforations so freely as it coats the upper and lower surfaces, the net result of two such coatings of 0.001 in thickness may be expected to provide the opposite walls of the opening each with a coating of not substantially more than 0.00 1" in thickness, thus providing a total reduction in the diameter of 0.002.

Since certain of the available plastic materials, such as, among them, Teflon, are characterized by having an extremely low coefficient of friction, together with great wear resistance, the coating of the perforated sheet material, as above described, has the very important advantage of forming a smooth integument extending across the joints in the material constituting the band and of enabling the new Fourdrinier wire to slide much more easily across the tops of the suction boxes than does the usual woven wire. Furthermore, such wear as does take place is distributed uniformly over the entire surface of this new Fourdrinier wire so that it does not become necessary to discard the wire nearly as quickly as is true of the woven wire where the wear is concentrated at the points at which the strands cross each other. Moreover, the lining of the holes with this smooth coating material helps to reduce the blocking of the holes with fibers or chemicals. It also makes cleaning, when necessary, much easier, it being noted that the coating material is chosen for its resistance to chemicals and acids so that the cleaning operation may be performed as often as desired and, by the use of any useful detergents, and most acids met with in paper-making, without reference to possible injury of the Fourdrinier wire. Obviously, the low coefiicient of friction of the coating material has the effect of reducing the wear on the suction box cover and other machine parts such, for example, as the rolls with which the Fourdrinier wire comes into contact. Moreover, the flatness and smoothness of the wire tends to produce a more uniform thickness of paper web and to make the removal of water by the suction boxes more efiicient.

While the material of the present invention is primarily designed for use in the making of an endless Fourdrinier Wire or belt, it is contemplated that the sheet material herein disclosed, whether coated or not, may be employed for covering the cylinder of a cylinder type paper-making machine.

Thus, for example, FIG. 15 diagrammatically shows a portion of such a machine, wherein the forming cylinder X turns within the pulp vat V, the peripheral surface of the cylinder X being of perforated sheet material, for example, like that of FIG. 6, and the endless belt T is held in position by the conical roll R to take the paper web from the cylinder X as it is formed.

While herein suggestions have been made as to certain desirable dimensions and as to material which have been found useful for the described purpose, it is to be understood that the invention is not to be limited to the precise dimensions or dimensional relationships hereinabove described, nor to the particular materials named, but is broadly inclusive of any and all modifications both of structure and method, which fall within the terms of the appended claims.

I claim:

1. An endless, pervious carrier operative to perform the function of the usual woven Fourdrinier wire of a conventional paper-making machine of the kind wherein said carrier is pulled at high linear velocity across a suction box cover, characterized in that that surface, at least, of the carrier which contacts the suction box cover is smooth as contrasted with that of the customary woven Fourdrinier wire thus minimizing frictional resistance to its motion and thereby reducing wear and prolonging its useful life, said endless carrier comprising a single ply of flexible, perforate sheet material of a uniform thickness of the order of 0.005" and having a tensile strength of the order of that of a conventional woven Fourdrinier wire whereby it is capable of withstanding the pulling strain to which it is subjected in use, the perforations in said sheet material being of uniform size and arranged in rows with the perforations in each row uniformly spaced apart and staggered relatively to those in the adjacent rows, the individual perforations being from 0.005" to 0.015" in diameter and being so arranged as to provide an aggregate of openings representing from approximately 20% to approximately 35.4% of the unit area of the original sheet material.

2. An endless pervious carrier according to claim 1, wherein the sheet material is metal and the perforations therein are of an average diameter of approximately 0.012" and wherein the sheet material has a smooth, tough, hard, flexible coating of an organic material having a coeflicient of friction of the order of that of Teflon adherent to that surface, at least, of the carrier which contacts the suction box cover, said coating having an aperture therein registering with each one, respectively, of the holes in the sheet material.

3. An endless pervious carrier according to claim 1 and which may be of a width of as much as 384 inches and of a length as great as feet and which comprises a plurality of individual perforate metal sheets having their adjacent edges permanently joined to provide a carrier of the de sired length and width, and a hard flexible coating of Teflon upon the upper surface of the carrier extending across the joints between the constituent plates thereby to provide a smooth uniform surface for the reception 'of the paper web.

References Cited in the file of this patent UNITED STATES PATENTS Arnold Oct. 16, Carmichael May 26, Sherwood June 25, Loetscher Dec. 30, Rafton Nov. 7, Richardson Feb. 11, Hausner June 2, Muller June 25, Mitchell et al Nov. 12, Bergstrom Nov. 25,

8 2,929,507 Kimline Mar. 22, 1960 2,946,731 Falls July 26, 1960 2,965,924 Hull Dec. 27, 1960 2,992,469 Hose et a1. July 18, 1961 OTHER REFERENCES 

1. AN ENDLESS, PERVIOUS CARRIER OPERATIVE TO PERFORM THE FUNCTION OF THE USUAL WOVEN FOURDRINIER WIRE OF A CONVENTIONAL PAPER-MAKING MACHINE OF THE KIND WHEREIN SAID CARRIER IS PULLED AT HIGH LINEAR VELOCITY ACROSS A SUCTION BOX COVER, CHARACTERIZED IN THAT THAT SURFACE, AT LEAST, OF THE CARRIER WHICH CONTACTS THE SUCTION BOX COVER IS SMOOTH AS CONTRASTED WITH THAT OF THE CUSTOMARY WOVEN FOURDRINIER WIRE THUS MINIMIZING FRICTIONAL RESISTANCE TO ITS MOTION AND THEREBY REDUCING WEAR AND PROLONGING ITS USEFUL LIFE, SAID ENDLESS CARRIER COMPRISING A SINGLE PLY OF FLEXIBLE, PERFORATE SHEET MATERIAL OF A UNIFORM THICKNESS OF THE ORDER OF 0.005" AND HAVING A TENSILE STRENGTH OF THE ORDER OF THAT OF A CONVENTIONAL WOVEN FOURDRINIER WIRE 